RIM products have been known in the art for a long time. Polyurethane materials were the first polymers to be used in the RIM process. Early systems consisted of polyether polyols, glycol chain extenders, catalysts and aromatic polyisocyanates. These systems exhibited problems such as low mold filling viscosity, long cycle times and the lack of a workable internal mold release capability.
The RIM materials which dominate the automotive market consist of polyether polyols, diamine chain extenders and aromatic polyisocyanates. These materials still suffer from relatively poor high temperature dimensional stability and internal release capabilities.
More recently RIM systems have been developed which consist of polyether polyamines, diamine chain extenders, such as DETDA and aromatic polyisocyanates. No catalysts are required in these RIM systems using polyether polyamines.
Representative patents describing the polyurea RIM systems include the following, assigned to Texaco Chemical Co.:
U.S. Pat. No. 4,297,444 PA1 U.S. Pat. No. 4,433,067 PA1 U.S. Pat. No. 4,444,910 PA1 U.S. Pat. No. 4,448,904 PA1 U.S. Pat. No. 4,474,900 PA1 U.S. Pat. No. 4,474,901 PA1 U.S. Pat. No. 4,487,908 PA1 U.S. Pat. No. 4,487,912 PA1 U.S. Pat. No. 4,499,254
U.S. Pat. Nos. 4,396,729; 4,444,910 and 4,433,067 concern elastomers prepared using a high molecular weight amine terminated polyether, an aromatic diamine chain extender and an aromatic polyisocyanate which may merely be a polyisocyanate or a quasi-prepolymer prepared from a polyol reacted with a polyisocyanate wherein some isocyanate groups are left unreacted. Various patents have been applied for and received using this basic combination as well as various mold release agents and other additives.
It would be a substantial advance in the art if new methods were developed to alter the properties of RIM materials in predictable ways and to vary the rate of reaction.